1. Field of the Invention
This invention relates to an ink jet printer wherein ink drops are applied to paper to effect desired printing.
2. Description of the Related Art
A general construction of an ink jet printer is shown as the related art in FIG. 4. A substantially U-shaped paper path 101 is formed so as to extend from a paper supplying station A to a paper discharging station B, and an ink jet head 102 is disposed in a printing station C intermediately of the paper path 101. The ink jet head 102 is moved in a direction perpendicular to the plane of FIG. 4 by a carrier not shown and jets drops of ink to paper to effect desired printing.
A feed roller 103 is disposed intermediately of the paper path 101. The feed roller 103 cooperates with a leaf plate 104 to feed cassette paper from a paper tray 106 positioned in the paper supplying station A or paper manually inserted into the paper path 101 to the printing station C. More particularly, the feed roller 103 rotates in the direction indicated by an arrow mark in FIG. 4 to transport paper pressed against it by the leaf plate 104 to the printing station C.
A paper discharging apparatus 110A is disposed at the last end of the paper path 101. The paper discharging apparatus 110A is provided to discharge paper (printed paper) after printing by the ink jet head 102 and includes a paper discharging roller 111 for transporting printed paper in a paper discharging direction (the direction indicated by an arrow mark E in FIG. 4), and a pinch roller 112 for resiliently pressing printed paper against the paper discharging roller 111. More particularly, the paper discharging roller 111 is mounted for rotation in the direction indicated by an arrow mark in FIG. 4 on the downstream side with respect to the ink jet head 102 in the paper transporting direction. The pinch roller 112 is mounted for resiliently pressing printed paper against the paper discharging roller 111 making use of the force of a spring or a like element. In order to prevent transfer of ink from printed paper to the pinch roller 112, the pinch roller 112 is formed as a pinch roller having a serrated outer circumferential face which has a smaller contacting area with printed paper. The pinch roller 112 is mounted for rotation on a pinch roller holder 113 by means of a support shaft 112a and is normally resiliently pressed against the paper discharging roller 111 by a spring 114.
In the ink jet printer of the structure described above, when the feed roller 103 rotates, paper held on the paper tray 106 is supplied into the paper path 101, and desired printing of the paper is performed by the ink jet head 102 in the printing station C. Then, the paper after printing is fed in the paper discharging direction (the direction of the arrow mark E in FIG. 4) by cooperation between the paper discharging roller 111 and the pinch roller 112 and is discharged into a paper receiving section 119 with the printed face thereof directed upwardly.
Several problems of the related art described above will be described subsequently. In the ink jet printer described above, in order to prevent soiling to paper which arises from transfer of ink to the outer circumferential face of the pinch roller 112, an ink absorbing member such as, for example, a blotter roller 129 for contacting with the outer circumferential face of the pinch roller 112 to absorb ink is sometimes provided as indicated by an alternate long and two short dashes line in FIG. 4. Normally, the blotter roller 129 is mounted for rotation on the pinch roller holder 113 by means of a support shaft 129a. The blotter roller 129, however, cannot completely prevent sticking of ink to the circumferential face of the pinch roller 112. Therefore, the circumferential face of the pinch roller 112 must necessarily be cleaned periodically.
Further, the blotter roller 129 is held in pressing contact under considerably strong force with the pinch roller 112 taking an error in working, an error in assembly and so forth into consideration. Consequently, the related art ink jet printer has a drawback that such a high rotational load may be applied to the pinch roller 112 that the pinch roller 112 may not rotate sufficiently upon feeding of paper, resulting in failure to smoothly discharge printed paper.
It is to be noted that, while development of the technique for preventing ink from sticking to the outer circumferential face of the pinch roller 112, such as, for example, a coating of the pinch roller 112 with a water repellent material to which ink does not stick readily such as, for example, a material of the TEFLON, has been and is being proceeded recently, it is impossible to completely prevent sticking of ink to the outer circumferential face of the pinch roller 112.